Rough-water towing system

ABSTRACT

A pusher towboat normally propels a load carrying vessel by pushing contact at the centerline of the stern of the vessel with a towboat-mounted shock absorbing pusher knee. A pair of tensioned rapidly detachable tiller lines interconnecting the vessel and the stern of the towboat lash the vessel and towboat together with a force substantially greater than the astern power of the towboat and stores energy in the pusher knee to rapidly separate towboat and vessel upon detachment of the tiller lines. A connected, but normally nonoperational, pull-towline enables pull-tow control of the vessel upon tiller line detachment. The points of connection of the tiller lines to the vessel, the point of pushing contact between towboat and vessel, and the points of connection of the tiller lines to the stern of the towboat lie in substantially the same horizontal plane. Relative length of the two tiller lines is adjustable under load but at equal tension, so that towboat thrust is available for steering the load carrying vessel by a variation in longitudinal alignment of the towboat with respect to the vessel.

114-253. )(R 3,645,225 SR United States Patent\ Lunde n51 3,645,225 :4Feb. 29,1972

[54} ROUGH-WATER TOWING SYSTEM [72) Inventor: Thomas '1. Lunde, 6Locksley Ave., San

. v. FranciscmCalif. 94122 {22; Filed: sem -1,1969

21} Appl.No.: 858.829

[52] US. Cl. ..ll4/235 R [51] Int. Cl ...B63b 21/00 [58} Field of Search..1 14/235, 77

{56] References Cited 'UNlTED STATES PATENTS 3,353,512 7 11/1967 Mathewset al .114/235 3,461,829 8/1969 Mosvold ..1 14/235 PrimaryExaminer-Trygve M. Blix Azzomey-Eckhoff and Hoppe 511 ABSTRACT A pushertowboat normally propels a load carrying vessel by pushingcontact at thecenterline of the stern of the vessel with v a towboat-mounted shockabsorbing pusher knee. A pair of tensioned rapidly detachable tillerlines interconnecting the vessel and the stern of the towboat lash thevessel and towboat together with a force substantially greater than theastem power of the towboat and stores energy in the pusher knee torapi-. };'}separate towboat and vessel upon detachment of the tillerlines. A connected, but normally nonoperational, pull-' towline enablespull-tow control of the vessel upon tiller line detachment. The pointsof connection of the tiller lines to the I vessel, the point of pushingcontact between towboat and yessel, and the points of connection of thetiller lines to the stern of the towboat lie in substantially the samehorizontal plane. Relative length of the two tiller lines is adjustableunder load but at equal tension, so that towboat thrust is available forsteering the load carrying vessel by a variation in longitudinalalignment of the towboat with respect to the vessel.

14 Claims, 16 Drawing Figures s. Maw

PATfNTEnreazmsrz r0 INVENTOR THOMAS T. LUNDE 7 I I j ATTORNtYS sum 2 ore v I NVENTOR.

THOMAS T. LUNDE ATTORNEYS PATENTEDFE-B 29 I972 SHEET 3 OF 6 INVENTOR.THOMAS T. LUNDE B"? h. @W W ATTORNEYS PAIENT'EDFEBZSWZ saw am 6 INVENTORATTORHFYS INVENTOR.

F i G B THOMAS T. LUNDE ATTORNEYS PATENTEBFEBNIBYB I 3.6455225 ISHEETSUFB FlG .15

INVENTOR. mums T. LUNDE ATTORNEYS ROUGH-WATER TOWING SYSTEMTbisapplication relates generally to methods and means for propellingload carrying essels by a towboat and more particularly r lates to asafe method and means for push-towing in rough watgxr.

' Heretofo e, towing of load carrying vessels, such as barges, in heavyseas has been accomplished by pulling the vessel with the towboat bymeans of a long pull-towline hanging substantially in a catenary toaccommodate instantaneous variations has been quite common in protectedwaters, even improved techniques, such as that disclosed in US. Pat. No.2,984,202 for Lmhing Arrangement for Pusher Towboat and Barge, becomeextremely dangerous in the rough water encountered results from theinability of these arrangements to cast off and rapidly separate towboatand barge, if necessary; or, from the dynamic load occurring uponreengag'ement of towboat and barge after a sea-caused'separation; or,from possible foundering ofa heavily laden tow.

The system of this invention normally lashes the towboat and barge inpushing contact without separation with highly tensioned tiller linesand simultaneously develops stored energy in the pusher knee toaugmentastem propeller thrust for rapid separation of the vesels shouldthe need arise to drop the tow at sea The lashing is rapidly detachableand carries resilient means for automatic takeup of variations in tillerline length caused by relative pitching, yawing, or rolling motionbetween vessels.

One object of the present invention is to provide a towing system inwhich the towboat can be cast off rapidly from the e laden vessel inrough weather and can be quickly and positively separated from it beforeany possible collision can occur.

Another object of this invention is to provide a method and meanswhereby the towboat can be cast off from its push-towing relation to theladen vessel and switched to conventional pull-towing with a deep seatowline if unusually rough weather or unsafe weather should occur andthen can easily resume the pushtow as such weather subsides.

5 construction shown in FIG. [2;

in off-shore or deep sea towing service. The danger in part FIG. 12 isatop plan view of a preferred embodiment in a knee construction forengaging the stern of a barge with a push-towboat;

FIG. l3 is a side elevation and partial section of the knee FIG. 14 is aplan view of a second embodiment in a quick release mechanism fordisconnectably securing tiller lines to a push-towboat;

FIG. 15 is an elevation ofa portion of the quick release canin forwardmotion of the two vessels. Although push-towing nectio'n' mk -1 15 fFIG.14*; and

FIG. 16 is an elevation illustrating positions for quick releasemechanism when the tiller lines are being disconnected from the pistonrod of a cylinder.

FIG. lillustrates a towboat l lashed in pushing relationship to a loadcarrying bfig'gby means of highly tensioned tiller ijllnesild'bri theport side and 3b on thestarbpard side, both lines eii tending from thestern of the towboat to thesternof the barge. Towboat' 1' makescontinuous pushing contact with barge 2 at its centerline by means of ashock-absorbing pusher knee 4 rigidly mounted on the bow of the towboat.Knee 4 essentially comprises a cylindrical casing 5 affixed to thetowboat and a plunger 6 which is reciprocable within the casing. Inaddition, plunger 6 bears against a shock absorbing coil spring 7 seatedwithin casing 5. The forward end of plunger 6 carries a button 8 thatengages a curved pusher bar 9 rigidly mounted on the barge stern headlogat its centerline. Bar 9 has a vertically elongated and curved cavity 10facing astem which receives the button 8. If desired, the pusher kneemay be provided with means forre tracting it aft when not in use.

tion of towboat and barge in FIG. I shows them in axial alignment;however, as will hereinafter be described, the stern of L A,....l.. A aL- -L:Po-J A... Q 0 --Lav .-J 2- --I a uni LUH'JJQL .31! Li 325E115 U.JUIL U! Dkfll will :1! uru os \L' make its propeller thrust availablefor steering the barge. The mating curved surfaces of the pusher button8 and pusher 0 socket cavity 10 accommodate changes in orientation rAn-ob ect of this invention also 15 to provrd ea push-towing 7 systemwhich towboat thrust is available for steering the between the towboatand barge.

While in push-towing service the tiller lines are tensioned so thatthetowboat and barge are continuously and firmly lashedl Toad carryingvessel by varying 'the angularity"betweeh towliiboatand vessel. V

Still th a m0 at object of the invention is to prov'de a method 4 threetimes the astern power of the towboat are used. The

into conta'E'fTvith ohe anotheplowlirigtensions in the order of 1 andmeans for changing tension in the tiller lines and for continuouslysensing the load in those lines while under way.

Other objects and advantages of this invention will become apparent froma consideration of the following detailed are identified by likereference numbers throughout.

FIG. I is a perspective view of the towboat and a barge showing thepushing relationship of the vessels;

FIG. 2 is a detail perspective view of one means for attaching thetiller lines to a barge;

FIG. 3 is a plan view of the stern of the towboat illustrating one formof quick release means and tension means for attaching the tiller linesto the towboat;

FIG. 4 is an elevational view taken along lines 4-4 of FIG.

FIG. 5 shows in plan one means for connecting the tiller line to thedrums of FIG. 3 taken alonglines 5-5 of FIG. 4;

FIG. 6 is a schematic diagram of'an hydraulic system used to tension thetiller lines;

porated in the tiller lines; I

F110. 8 is a partial sectional view of the same spring means taken alonglines 8-8 of FIG. 7;

FIG- 9 is a diagrammatic plan view showing the push-towsteering thebarge;

FIG. 23 is a diagrammatic plan view showing the push-towboat shortlyafter it has cast off from the barge;

towing relationship with the barge;

1 FIG. 11 is a diagram of thepush-towboat moved into andin 75 each to agrooved wire rope drum 31a, 31b rotatably mounted spring 7 in the pusherknee is designed so that under such loading it is compressed toapproximately half of its fully extended length for two purposes, firstto absorb any shock loaddescripfion and the accompanying drawingswherein kc pans ing between barge and towboatwhich might occur andsecond headlog which defines a vertical channel 14 in which is carriedan adjustable carrier 15 suspended by a positioning chain loop 16trainingover an uppersprock t 17 and a lower sprocket 18 mounted at theends of channel 14. To the stern side of the carrier is attached lashingeye 19 to which the spring means FIG. 1 is a partial sectignal view ofthe pring means incor- 11a, 11b on the end of I18 KIIICI IIIICS arepinned. Vertical elevation of the eye and its carrier can be varied byrotation of tr a chain sprockets, manually for example before lashing,so that the points of connection at" the spring means to the barge, theconnections of the tiller lines to the stern of the towboat boat and abarge in push-towing relation using boat thrust for and the point ofcontact between the pusher knee button and the socket cavity lie insubstantial; the some horizontal plane.

l I.! ..Z. In .-.J L. H.L aL- -L-I Aw-s l1 lUbKlllB Pl" IV Paaeu'lg\IIIUUGH LII: puaruuuurs Lllfllll lw? secures the carrier at anypredetermined elevation.

Tiller lines 3a, 3b are anchored at the stern of the towboat,

float the end of the tiller lines so that they can be easily recovered.Also mounted on the stern of the towboat is a pair or cylinders ortension means 33a, 33b by means of which drums 3la, 31); respectivelycan be rotated to wind the tiller lines onto the drums and tension them.Each tension means may be selectively operated as to lash towboat andbarge together or to pay out the tiller lines until they automaticallydetach from the drums and are dropped. I

As is more clearly illustrated in FIGS. 3, 4 and 5, the port andstarboard tiller line drums 31a, 31b are rotatably mounted;

on the main deck of the towboat. In the embodiment shown, each tillerline is wound on the lower grooves of the drum with the end of each linesecured to the drum by a slip fitting 3412 which bears against aretainer 35b on the drum, this being shown in FIG. 5. lt will be readilyseen that rotation of the drums as to pay out the tiller lines willeventually release the fittings and drop the tiller lines.

As indicated above, each of the tiller line drums is rotated by one ofthe tension means 33a, 33b, each tension means comprising an hydrauliccylinder 36a, 36b carrying a piston 37a. 37b mounted on the end of apiston rod 38a, 38b. The rods carry a sheave block 39a, 39b at theirfree ends, and each block takes a multiple purchase on a drum 31a, 31b,by means of: tensioning cable 4011,40 wound on the top of a drum. in

'the three-part purchase shown, one end of the tensioning cable is fixedto a block 39a, 39b, and each cable is entrained over a deck-mountedfixed block 41a, 41b, then around the sheave on the end of a piston rod38a, 38b and onto the top of a tiller line drum 31a, 31b. Accordingly,retraction of either piston rod 38a, 38b takes up and/or tensions theassociated :ikr tine whereas extension of either red cave out the tillerline, and both rods may be extended to a point that the tiller lines 3aand 3b are disconnected and dropped.

FIG. 6 schematically shows one form of hydraulic tiller line controluseful in actuating the port and starboard tiller line tension means33a, 33b. The hydraulic control comprises a source of hydraulic pressure50 which communicates through block valve with the rod side of cylinder36a and through block valve 52 with the rod side of cylinder 36b. Theblind sides of cylinders 36a. 36b communicate with each other and alsowith an elevated reservoir 54 through a block valve 53. Three-way valve55 through associated conduits connects the rod sides of both cylinderstogether and to both cylinder blind sides. Throttle valves 56 and 57also communicate the rod side of cylinders 36a and 36b. respectively, toits blind side and to that of the other cylinder.

The system is at equilibrium with block valves 51, 52 closed. To connectthe tiller lines to the barge, block valve 51, and/or 52, is opened andthree-way valve 55 is opened while block valve 53 and both throttlevalves 56, 57 remain closed. The resuiting differential pressure acrossthe pistons in cylinders 36:: and 36b causes the piston rods to extend,enabling the tiller lines, pinned to the lashing eye on the barge, to beattached to their respective drums.

The port side tiller line may then be taken up by opening block valves53 and 51 and closing the remainder of valves 52, 55. 56 and 57. Thehigh pressure on the rod side of cylinder 36a retracts piston rod 38a toa predetermined position or pressure setting which may be read on a portside pressure gage 58. This gage may be calibrated in terms of pressurebut it is also desirable to provide a scale for reaching thecorresponding value of tiller line tension. Excess oil from the biindside of cylinder 36a flows to reservoir 54.

Starboard tiller line 36 may be taken up in similar fashion by openingblock valves 53 and 52 and closing all other valves,

sure gage S9.

' While under way,'the stern of the towboat may be maneuvered to port byretracting port side piston rod 380 and extending that on the starboardside. This is done by opening block valves 51 and 53, closing valves 52,55 and '56. and opening throttle valve 57. In this manner the pressuresource is open to the rodtside of the takeup cylinder 36a. hydraulicfluid bleeds from the rod side on the other cylinder through thethrottle valve 57 to the lower pressure level of reservoir 54. Thetakeup cylinder retracts while the other extends. and

the stern of the vessel swings in response to the stroking cylinders. Ina similar mannen'the stern of the towboat may be maneuvered to starboardby retracting the starboard piston rod and extending the port rod byopening block valves 53 and 52 and throttle valve '56 while closingblock valve 51, threeway valve 55 and throttle valve 57.

. The hydraulic control system may be operated to disconnect both tillerlines from drums 31a and 311; by moving both pistonsin cylinders 36a and3617 from retracted to extended positions. This is accomplished byopening block valve 5i (and/or block valve 52) and three-way valve 55,and by closing block valve 53 and both of the throttle valves 56 and 57.The differential pressure across the pistons causes the cylinder rods toextend.

It is also contemplated that the tiller lines may be disconnectedwithout aid of hydraulic pressure by opening ail valves but the throttlevalves and by putting the towboat in reverse. The movement of thetowboat (which produces tension in the tiller lines) will cause drums31a and 31b to rotate while forc to quickly separate the vessels uponcasting them off. in addition, the stern of the towboat may be easilymaneuvered while under way to steer the barge. As an important safetyfeature,

the tiller line tension may be ascertainedat all times by reading thepressure on gages 58, 59.

Referring to FIGS. 7 and 8, a spring means suitable for use at theforward end of each tiller line comprises a plurality of resilientcushion pads 60 compressed within the bight of a loop formed in the endof the tiller line and a U-shaped frame 61. As shown, the end oftillerline 3a is clamped in a loop by a wire rope clamp 62, and frame 61 ismade from a'steel rod bent into a generally U shape and orientedreiative to the loop. The closed orbent end of the rod supports a pairof washers 63 which are welded thereto to form the stop for acompression plate 64 and define an attachment eye 65 that may be pinnedto the tiller lashing eye 19 on the barge. Cornpression plate 64 isslidably mounted upon the two frame legs and within the end loop of thetiller line, a groove being formed in the compression plate forreceiving the end loop. A plurality of cushion pad spacers 66. eachhaving semicircular cutouts which fit the legs of the frame 61. are alsodisposed within the loop of the tiller line, a pair of cushion pads 60(which are substantially donut shaped and made of a resilient hardrubber) being disposed between each pair of spacersv A keeper plate 67(withirfthe ti-ller line loop but also slid able on the legs of frame6!) bear against the end most spacer. This keeper plate is held in placeby nuts 68 threaded on the free ends of frame 61.

Compression plate 64, cushion pad spacers 66, and cushion pads 60 (aswell as keeper plate 67) are each slidable along the legs of frame 61.within the end loop of the tiller line. with no tension on the tillerline they may occupy the positions illustrated in FIG. 3, the cushir 4by tightening nuts 68. As tension l5 tnereattc tiller lines, the cushionpads are compressed. The degree of compression is dependent upon thetension applied and this changes to accommodate relative pitching,rolling, and other motions between the towboat anc barge.

our

One of the important features of the present invention is the immediateability to convert from push-towingto pull-towing in the event thatextremely rough water makes it dangerous'to continue a push-towingrelationship between towboat and barge. in FIG. 9 towboat l is inpushing relationship-to the 5 load carrying vessel 2 and pusher knee 4is in contact with bar 9 on its stern centerline. Tiller lines 3a, 3bsecurely lash boat 1 to barge 2. The centerline of the towboat may bealigned. with 'the centerline-of the bargeor it'may have an angularrelationship with respect to the barge centerlineso that tug thrust isavailable for steering the barge. Both conditions are illustrated in H6.9. The distance R, as shown, represents the moment arm that is availablefor turning the barge with propeller thrust, the resultant turningcouple being in addition to the l 10 and 11. First, the combination oftowboat and barge is brought about to a steady course generally into theweather and the towboat is put into full reverse. The tiller lines arethen quickly cast off as hereinbefore described and the energy stored inthe pusher knee spring assists in positive separation of the two vesselsin spite of such uncontrollable variables as stern power, wind, weatherand sail area'of the two vessels. The two tiller lines detach from theirdrums and are dropped into the sea. Their free ends remain accessiblefor later pickup by buoys32a, 32b. The towboat rapidly separates fromthe bargeand the danger which otherwise would be associated 35 withcasting off from a heavy and massive free floating barge is eliminated.The towboat is then positioned, as shown in H68. 10 and 11, inpull-towing relationship to the barge, towline 70 now being used to pullthe barge until the heavy seas subside.

At that time the deep sea towline can be stowed and the towboat canreassume push-towing relationship by picking up the tiller lines 30, 3bwhich trail behind the barge attached to buoys 32a, 32b. If desired, anauxiliary towline 72 may be triced to the starboard side of the bargewith a trailing buoy at its endasat 83.

FIGS. 12 and 13 illustrate a preferred embodiment in a shock absorbingpusher knee 4a that includes a ball-andsocket joint. This kneeconstruction provides a superior contact with the barge and toleratesvarious combinations of movement between tug and barge includingsimultaneous pitching and rolling. Pusher knee 4a is also useful indampening-vertical motion between barge and pusher tug. Such motion iscaused primarily by the pitching of the two vessels. but it may also beattributed to surge. Since the magnitude of these forces is generallytoo great to restrain completely, it is essential that there be somevertical give between the barge and pusher tug. On the other hand, toomuch give" or. freedom of movement between the vessels makes the pushingoperation difficult, and if there is too much relative movebow of apusher tug in lieu of the cylindrical casing 5 of knee 4. Ball 80supports a brakeshoe comprising a socket plate 83 and a pair of ringplates 84 and 85. Plate 84 is peripherally welded to the face of plate85 which is in turn connected to socket plate 33 by a plurality of bolts86. Thus, the brakeshoe is mounted to ball 8G for universal movement asis customary with a standard balland-socket connection.

Socket plate 83 is especially formed with top and bottom extensions 83::and 83!), respectively, these extensions being provided to facilitateand maintain engagement of the shoe with bar 9 mounted on the bargestern headlog. The cross section of the bar is illustrated generally bythe broken lines in P10. 12, said bar comprising a pair of parallelcontact. rails 90 and 9b and having a cavity 10 that receives extensions83a, 83b. 9

Socket plate 83 further supports a pair of brake linings 87, each liningbeing bonded or attached to a support plate 88 which is in tum mountedto plates 83 and by a plurality of bolt connections 89. in operation,brake linings 87 make coni wtact with the pair of rails'9c, 9b'forpushing the barge; and,

its coefficient of friction, thereby controlling one of the twovariables which affect relative movement between the linings and rails9a, 9b. The second variable is the contact pressure between the liningsand rails and this may be regulated by ad justing tiller line tension.This tension may be varied to suit weather or other operatingconditions, so long as. the minimum tension is high enough to prevent aseparation between linings 87 and rails 9a, 9b.

Sleeve 81 is adapted to be moved into housing 82 against the resilientbias imposed by a plurality of cushion pads 90 housed within sleeve 81between a stop plate 91 and the interior wall 81a of sleeve 81. Plate 91is mounted to the vertical centerline plate 910 that forms a structuralpart of the bow section of the pusher tug. As shown, plate 91 is alsolodged within sleeve 81, the peripheral edges of the plate being engagedby one end of a keeper sleeve, 92, also disposed within the end ofsleeve 81 and secured thereto by bolt connections 93. Keeper sleeve 92is bolted to sleeve 81 while cushion pads 90 are slightly compressedbetween stop plate 9i and interior wall 81a. Thus, pads 90 are preloadedand tend to maintain the end of keeper sleeve 92 against the backsurface of plate 91 until pushing contact is made between the brakeshoeand the bar 9 on the barge.

In operation, a movement of sleeve 81 toward the left cornpressescushion pads 90 which then impose a resilient bias urging sleeve 81 tothe right.

Means is further provided for supplying a constant supply of lubricantbetween the surfaces of ball 80 and socket plate 83. For this purpose,ball 80 is formed with a hollow recess and a plurality of openings whichcommunicate that recess with the v spherical concave surface of socketplate 83. A continuous supply of lubricant may then be fed into thehollow recess of the ball through a conduit 94 connected to a mainreservoir stored on the pusher tug.

FIGS. 14-16 illustrate a second embodiment in a quick release device fordisconnecting tiller lines 3a and 3b from pusher tug 1. This embodimentdispenses with the need of a winding drum and a multiple part purchaseas used with the first described apparatus. However, the same hydrauliccircuitry illustrated in FIG. 6 may also be used with this secondembodiment.

Referring to FIG. 14 in particular. each tiller line is entrained arounda deck sheave 95 mounted near'the stern of tug l. The end of each tillerlineis provided with a bulbous fitting 96 which may be engaged and heldbetween a pair ofjaws 97a and 97!) forming a part of a clamshcll"fitting 97. This fitting is attached to the end of a piston rod 98 whichmay be reciprocated and forming a part of hydraulic cylinder 99. Thiscylinder may be identical to cylinders33a, 33b used in con nection withthe first described quick release apparatus.

Jaws 97a and 97!: are each pivoted on parallel axes. and each jaw ispivoted to an open 61:; :hm forced agair t a splitter 100. In the formillustrated, splitter lull comprises two parts 100a and 100b, one partbeing spaced from the other a distance greater than the width of fitting96 but a distance less than the width of clamshell fitting 97. inaddition, each part of splitter 100 is formed with convergent surfacesthat define all,

camming edges 1000 for wedging jaws 97a and 97b apart and into openposition as piston rod 98 drives the clamshell fitting $7 into contacttherewith. This operation and position of elements is most clearlyapparent in view of FIG. 16.

M s is further provided for clamping jaws 97a and 97b onto r tting 96and then maintaining such engagement until such time that the fitting isto be released. This means essentially comprises two pairs of upper andlower rails 101 and 102. respectively, each rail having an out-turnedend 1010,

I022: in the vicinity of splitter I00. Rails 10] and'102extend parallelto piston rod 98 and are so positioned relative to jaws 97a and 972;that the jaws can open only when they are positioned adjacent thesplitter. It will be further apparent that a retraction of piston rod 98will bring jaws 97a and 97b into contact with the end of rails 101 and102, causing the jaws to be pivoted to a closed position and allowingthe clamshelF to described for applying tiller line tension and varioustypes of resilient means may be used as a substitute for tiller linesprings and knee cushions.

What is claimed is: l. A methodjg rough-water towing of a load carryingves- 5. The system. of claim 4, the points of connection of saidresilient tension means to said vessel and to said towboat and thecontact of said pusher means with said vessel being in substantially thesame horizontal plane.

6. The system of claim 4, said towboat and vessel being relativelyrotatable about a longitudinal axis through the point of said pushingcontact. said resilient tension means being lengthened and shortened toaccommodate such rotation.

7. The system of claim 4, said pusher means comprising a reciprocableplungerandmeans resiliently urging said plunger in a forward direction;said pair of tension means comprising a pair of tiller lines and a pairof resilient means connected in se ries with each tiller line,respectively, for extending and retracting the effective line length;and means for separately tensioning each tension means as to take up orpay out each tiller line.

8. The system of claim 4, said pusher means comprising a reciprocableplunger, means resiliently urging said plunger in a forward direction.and a contact shoe mounted for universal movement on the forward end ofsaid plunger.

9. The system of claim 4, said pusher means comprising a contact shoe,said shoe having a pair of laterally spaced and parallel contactsurfaces engageable with complementary spaced and parallel contactsmounted on the stem end ofsaid vessel.

10. The system ol'clairn 4, said pusher means comprising a reciprocableplunger. means resiliently urging said plunger in a forward direction.and a contact shoe mounted to the forward end of said plunger. said shoehaving an extension pro jecting in a forward direction and a pair oflaterally spaced and set by a t o wboat comprising propellingsai dvggsel by pushing a contact with said towboat at the'stem centerline ofsaid vessel; detachably lashing said towboat and vessel together; andten-. siorting the lashing with a force sufficient to prevent separationof said vessel and towboat and concomitantly developing by said forcepotential energy'ihcluding a rearwardly directed major componentsubstantially instantaneously variable as a fl'g'ific'tidrifofthetension in said lashing for quickly'pushing said vessel and towboatapart upon detachment of said lashing. I

2. A method according to claim 1 including the step of resilientlylashing said towboat and vessel togetherto accor mo 33g jffrentialrolling or pitching between vessel and towcarrying vessel by a towboatcomprising normally maintaining slack tow means interconnected betweenthe bow of said vessel and said towboat; normally propelling said vesselby pushing contact with said towboat at the stern centerline of saidvessel; detachably lashing said towboat and vessel together with a forcesufficient to prevent separation of said vessel and towboat; developingby said force potential energy for quickly pushing said vessel andtowboat apart upon detachment of said lashing; quickly unlashing saidtowboat and vessel thereby releasing said potential energy to push saidvessel and towboat apart while simultaneously reversing said towboat;maneuvering said towboat forwardly of said vessel; and then tensioningsaid tow means for pulling said vessel with said towboat.

4. A system for rough-water towing of a load carrying vessel with atowboat comprising pusher means on said towboat normally in pushingcontact with said vessel at its stern; a pair of resilient tensionmeans, one connecting the stern of said towboat with the port side ofthe stern of said vessel and the other connecting the stern of saidtowboat with the starboard side of the stern of said vessel; means fortensioning said tension means; means for quickly detaching each of saidtension means from said towboat; and means associated with said pushermeans for storing energy including a rearwardly directed major componentsubstantially instantaneously variable as a function of the tension insaid tension means tending to separate said towboat and vessel forpushing said towboat and vessei apart upon detachment of said tensionmeans.

parallel contacts disposed on opposite sides of said extension; wherebysaid extension is adapted to be engaged with a recess provided on thester'n'end of said vessel to maintain said laterally spaced and parallelcontacts in engagement with complementary contacamounted on said vessel.

11. The system of cl 4, said means for quickly detaching tension meansc: r I a tiller tit: and a slip fitting secured to one end of saidtiller line, a rotatable drum mounted at the stem end of said tug fortaking up and paying out said tiller line, a retainer mounted to saiddrum and engageable with said slip fitting for selectively anchoringsaid tiller line to the drum or allowing said slip fitting to fall awayfrom the drum when said tiller line is fully unwound from the '31'5method of switching from push to pull towing of a load 4 5 drum, andpower means for rotating and latching said drum.

12. The system of claim 4, and further comprising means for 'selectivelysecuring one end of each tension means at a predetermined elevation tosaid load carrying vessel to direct the force of said tension means insubstantially horizontal planes.

13. The system of claim 4. and further comprising hydraulic controlsincluding a pair of fluid operated cylinders releasably connectable withsaid pair of tension means, respectively, each of said cylinders havinga throw sufficient to lengthen or shorten the associated tension meansto create an angularity between the centerlines of said vessel and saidtowboat for steering.

14. A system for rough-water towing of a load carrying vessel with atowboat comprising pusher means on said towboat normally in pushingcontact 'with said vessel at its stern; a pair of resilient tensionmeans. one connecting the stern of said towboat with the port side of astern of said vessel and the other connecting "to star." 7 idtcxs'hoatwith the starboard side of the stern of said was means for tensioningsaid tension means; and means or v ly detaching each of said tensionmeans from said towboat comprising a first fitting secured to one end ofsaid tension means, a ciamshell fitting having pivoted jaws for engagings id first fitting, power means for reciprocally moving said .shellfitting, and a splitter disposed in the path ofmovernent for saidclamshell fitting and adapted to be eng ed 51:; string for separatingsaidjaws to release said tits

1. A method for rough-water towing of a load carrying vessel by atowboat comprising propelling said vessel by pushing contact with saidtowboat at the stern centerline of said vessel; detachably lashing saidtowboat and vessel together; and tensioning the lashing with a forcesufficient to prevent separation of said vessel and towboat andconcomitantly developing by said force potential energy including arearwardly directed major component substantially instantaneouslyvariable as a function of the tension in said lashing for quicklypushing said vessel and towboat apart upon detachment of said lashing.2. A method according to claim 1 including the step of resilientlylashing said towboat and vessel together to accommodate differentialrolling or pitching between vessel and towboat.
 3. A method of switchingfrom push to pull towing of a load carrying vessel by a towboatcomprising normally maintaining slack tow means interconnected betweenthe bow of said vessel and said towboat; normally propelling said vesselby pushing contact with said towboat at the stern centerline of saidvessel; detachably lashing said towboat and vessel together with a forcesufficient to prevent separation of said vessel and towboat; developingby said force potential energy for quickly pushing said vessel andtowboat apart upon detachment of said lashing; quickly unlashing saidtowboat and vessel thereby releasing said potential energy to push saidvessel and towboat apart while simultaneously reversing said towboat;maneuvering said towboat forwardly of said vessel; and then tensioningsaid tow means for pulling said vessel with said towboat.
 4. A systemfor rough-water towing of a load carrying vessel with a towboatcomprising pusher means on said towboat normally in pushing contact withsaid vessel at its stern; a pair of resilient tension means, oneconnecting the stern of said towboat with the port side of the stern ofsaid vessel and the other connecting the stern of said towboat with thestarboard side of the stern of said vessel; means for tensioning saidtension means; means for quickly detaching each of said tension meansfrom said towboat; and means associated with said pusher means forstoring energy including a rearwardly directed major componentsubstantially instantaneously variable as a function of the tension insaid tension means tending to separate said towboat and vessel forpushing said towboat and vessel apart upon detachment of said tensionmeans.
 5. The system of claim 4, the points of connection of saidresilient tension means to said vessel and to said towboat and thecontact of said pusher Means with said vessel being in substantially thesame horizontal plane.
 6. The system of claim 4, said towboat and vesselbeing relatively rotatable about a longitudinal axis through the pointof said pushing contact, said resilient tension means being lengthenedand shortened to accommodate such rotation.
 7. The system of claim 4,said pusher means comprising a reciprocable plunger and meansresiliently urging said plunger in a forward direction; said pair oftension means comprising a pair of tiller lines and a pair of resilientmeans connected in series with each tiller line, respectively, forextending and retracting the effective line length; and means forseparately tensioning each tension means as to take up or pay out eachtiller line.
 8. The system of claim 4, said pusher means comprising areciprocable plunger, means resiliently urging said plunger in a forwarddirection, and a contact shoe mounted for universal movement on theforward end of said plunger.
 9. The system of claim 4, said pusher meanscomprising a contact shoe, said shoe having a pair of laterally spacedand parallel contact surfaces engageable with complementary spaced andparallel contacts mounted on the stern end of said vessel.
 10. Thesystem of claim 4, said pusher means comprising a reciprocable plunger,means resiliently urging said plunger in a forward direction, and acontact shoe mounted to the forward end of said plunger, said shoehaving an extension projecting in a forward direction and a pair oflaterally spaced and parallel contacts disposed on opposite sides ofsaid extension; whereby said extension is adapted to be engaged with arecess provided on the stern end of said vessel to maintain saidlaterally spaced and parallel contacts in engagement with complementarycontacts mounted on said vessel.
 11. The system of claim 4, said meansfor quickly detaching said tension means comprising a tiller line and aslip fitting secured to one end of said tiller line, a rotatable drummounted at the stern end of said tug for taking up and paying out saidtiller line, a retainer mounted to said drum and engageable with saidslip fitting for selectively anchoring said tiller line to the drum orallowing said slip fitting to fall away from the drum when said tillerline is fully unwound from the drum, and power means for rotating andlatching said drum.
 12. The system of claim 4, and further comprisingmeans for selectively securing one end of each tension means at apredetermined elevation to said load carrying vessel to direct the forceof said tension means in substantially horizontal planes.
 13. The systemof claim 4, and further comprising hydraulic controls including a pairof fluid operated cylinders releasably connectable with said pair oftension means, respectively, each of said cylinders having a throwsufficient to lengthen or shorten the associated tension means to createan angularity between the centerlines of said vessel and said towboatfor steering.
 14. A system for rough-water towing of a load carryingvessel with a towboat comprising pusher means on said towboat normallyin pushing contact with said vessel at its stern; a pair of resilienttension means, one connecting the stern of said towboat with the portside of the stern of said vessel and the other connecting the stern ofsaid towboat with the starboard side of the stern of said vessel; meansfor tensioning said tension means; and means for quickly detaching eachof said tension means from said towboat comprising a first fittingsecured to one end of said tension means, a clamshell fitting havingpivoted jaws for engaging said first fitting, power means forreciprocally moving said clamshell fitting, and a splitter disposed inthe path of movement for said clamshell fitting and adapted to beengaged by said fitting for separating said jaws to release said firstfitting.